Communication systems and methods having reduced frame duration

ABSTRACT

A transmitter arrangement using randomization is disclosed. The arrangement includes one or more randomizers, a measure component and a frame select component. The one or more randomizers are configured to generate one or more randomized frames from an original frame. The measure component is configured to measure a criterion for the original frame and the one or more randomized frames. The frame select component is configured to select a frame for transmission from the one or more randomized frames and the original frame. The selection is performed according to the measured criteria, such as frame duration.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 14/587,089, filed on Dec. 31, 2014, the contents of which areincorporated by reference in their entirety.

BACKGROUND

Communication protocols are used to facilitate communications betweencomponents and devices. The communication protocols provide astandardized way for the transfer of information.

Typically, the protocols utilize frames to transfer the data and eachframe requires a period of time to be transferred, which is referred toas the frame duration. The frames can vary in duration according to thedata provided in the frames and the protocol being used. Thus, someframes have a relatively long or large duration while others have ashorter duration. Unfortunately, the system must assume the worst casescenario and use the maximum frame duration for communications. Thislowers throughput and generally degrades communications.

What is needed is a technique to reduce frame duration and increasecommunications throughput.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a system that mitigates frame durationusing randomization.

FIG. 2 is a diagram illustrating a randomizer transmitter that mitigatesaverage frame duration.

FIG. 3 is a diagram illustrating a derandomizer receiver that handlesrandomized frames.

FIG. 4 is a diagram illustrating an example frame for transmission.

FIG. 5 is a graph illustrating example simulation of frames sent usingrandomized frames and non-randomized frames.

FIG. 6 is a flow diagram illustrating a method of transmitting frameswith a reduced average duration.

DETAILED DESCRIPTION

The systems and methods of this disclosure are described with referenceto the attached drawing figures, wherein like reference numerals areused to refer to like elements throughout, and wherein the illustratedstructures and devices are not necessarily drawn to scale.

FIG. 1 is a diagram illustrating a system 100 that mitigates frameduration using randomization. Randomization is used toscramble/randomize a frame using one or more seed values. Then, thescrambled frames are compared with the original frame with regard toduration and the shortest frame is used for communication. The system100 can also be considered an arrangement of the described componentsand variations can include additional components and/or omit one or moreof the included components.

The time period for a given frame to be sent is referred to as itsduration or frame duration. For various protocols, such as short pulsewidth modulation code (SPC) and single edge nibble (SENT), frameduration is a function of the data content of the frame. In one example,the duration of a frame in unit time (UT) is given by:t(UT)=56+Σ_(i=1) ^(n)(12+d _(i))

Thus, the frame has a fixed portion (56) and a variable portion. Forthis example, the frame has a frame duration with a minimum of 188 microseconds and maximum of 353 micro seconds, where n (number of nibbles) isat 11 and one unit time is 1 μs. If a worst case scenario is assumed,other systems would assume the maximum of 353 micro seconds for allframes, thereby limiting throughput. The variable portion depends on thenumber of nibbles and the content of the nibbles. A nibble is 4 bits.Thus, a nibble of “1111” results in a longer duration than the samenibble of “0000”. The duration of the “0000” nibble is 12UT, while theduration of the “1111” nibble is 27UT (=12+15).

The system 100 includes a data source 102, a randomizer transmitter 104,a derandomizer receiver 106, a component 108 and a control unit 116. Thesystem 100 mitigates frame durations in order to increase throughput andimprove communications. The data source 102 provides an original frameof data 110 having a fixed length or size. The frame 110 follows aprotocol, such as the SPC or SENT, and has a header, a fixed dataportion and a variable data portion. The data portions, in one example,are organized in nibbles, which are 4 bits of data.

The randomizer transmitter 104 receives the frame 110 and generates oneor more scrambled/randomized frames using pseudo-randomization andseeds, where one seed is used per scrambled frame. Thus, a plurality ofseeds are used to generate the one or more randmomized/scrambled frames.The randomized frames can include non-randomized portions, such as toinclude header information, such as sync information, seed indexes, andthe like.

A variety of scramblers/randomizers and types can be used to generatethe one or more randomized/scrambled frames. One technique involvesrandomly selecting bits of a data portion of the frame 110 to invert. Asan example, an additive scrambler/randomizer can be used that transformsthe data portion of the frame 110 by applying a pseudo-random binarysequence (PRBS). A linear feedback shift register can be used totransform the frame 110. As another example, a multiplicativescrambler/randomizer can be used. The multiplicative randomizer performsa multiplication of the frame 110 by a transfer function in Z-space. Itis appreciated that other suitable randomization techniques can be used.

The control unit 116 is configured to select or generate the seeds usedto generate the randomized frames. Additionally, the control unit 116 isconfigured to select or develop the randomization techniques used. Thiscan be performed during normal use or in development or initialization.For example, the control unit 116 can be configured to select seeds thatare more likely to result in shorter frame durations. Similarly, thecontrol unit 116 can be configured to select randomization/scramblingtechniques likely to result in shorter frame durations. Additionally,the control unit 116 can be configured to select the number of theplurality of seeds used and randomized frames generated. The more framesthat are used, the more bits required to identify the seed used togenerate the randomized frame, which can increase frame duration. In oneexample, two bits are used to index for 3 seeds and 3 generatedrandomized frames. In another example, a nibble of 4 bits is used toindex for 15 seeds and 15 generated randomized frames. It is appreciatedthat other suitable numbers of seeds and/or randomized frames can beused.

The randomizer transmitter 104 determines and compares the durations ofthe scrambled frames and the original frame 110 and generally selectsthe frame with the shortest frame duration. It is possible that theoriginal frame 110 comes out to have the shortest duration. The selectedframe 112 is sent by the transmitter 104. A seed indicating which, ifany, of the one or more randomizers used is pre-pended or otherwiseattached to the selected frame 112. In one example, a nibble of the dataportions is used for the seed index and is not randomized or altered.

Although the selection criterion of frame duration is shown, it isappreciated that other selection techniques or criteria can be used. Forexample, current consumption (for DSI3), numbers of transitions (forPSI5), and the like can also be used as selection criteria.Additionally, it is appreciated that multiple criteria can be used as aselection technique.

The derandomizer receiver 106 obtains the selected frame 112 using asuitable technique. The derandomizer receiver 106 is configured toidentify the seed used and descramble the selected frame. In oneexample, the receiver 106 is configured to identify the seed byidentifying an unrandomized nibble of the frame 112 and extracting thenibble to obtain the seed index. The derandomizer receiver 106 includesone or more derandomizers to perform the descrambling. The one or morederandomizers correspond to the one or more randomizers of therandomizer transmitter 104. Thus, for example, additive derandomizerscan be used to descramble the frame 112.

The derandomizer receiver 106 analyzes the frame 112 to identify theseed used, if any, to scramble the frame 112. In one approach, the seedindicates which derandomizer to use and the indicated derandomizer isused to descramble the frame 112. In another approach, all of the one ormore derandomizers generate one or more descrambled frames and the seedindicates which one of the descrambled frames to use. Variations ofthese approaches can also be used.

Thus, the derandomizer receiver 106 is configured to generate adescrambled or derandomized frame 114 using one of the above approachesand the seed. The descrambled frame 114 is substantially identical tothe original frame 110. The descrambled frame 114 is provided to thecomponent 108, which obtains and/or uses the fixed and variable datacontained therein.

The system 100 can continue operation with additional data frames, usedsequentially as the original frame 110. On average, the frames using therandomizer transmitter 104 tend to have a smaller duration and increasethroughput.

FIG. 2 is a diagram illustrating a randomizer transmitter 200 thatmitigates average frame duration. The randomizer transmitter 200receives a frame and generates a frame for transmission that mitigatesframe duration. The transmitter 200 can be used in the system 100 aboveas the randomizer transmitter 104 and/or other communication systems.

The randomizer transmitter 200 includes a plurality of randomizers 214,a plurality of measuring components 216 and a frame select component218. An original frame 110 is received by the transmitter 200. Theoriginal frame 110 is also received by the plurality of randomizers anda first of the measuring components 216.

The plurality of randomizers 214 scramble or randomize the originalframe to generate a plurality of randomized frames. Each of therandomizers uses a unique seed for performing the randomization. Thus,the generated randomized frames are typically varied in content and maybe varied in duration. Some examples of suitable techniques aredescribed above.

A suitable randomization or scrambling technique is used, such aspseudo-randomization. One technique involves randomly selecting bits ofa data portion of the frame 110 to invert, where the selected bitsdepend on the seed. As another example, an additive randomizer can beused that transforms the data portion of the frame 110 by applying apseudo-random binary sequence (PRBS). The randomizers 214 canincorporate a linear feedback shift register can be used to transformthe frame 110. As another example, a multiplicative randomizer can beused. The multiplicative randomizer performs a multiplication of theframe 110 by a transfer function in Z-space. It is appreciated thatother suitable randomization techniques can be used.

In this example, a first randomizer of the plurality of randomizers 214generates a first randomized frame using a first seed. A secondrandomizer generates a second randomized frame using a second seed and athird randomizer generates a third randomized frame using a third seed.

The measuring components 216 measure a duration of the original frameand the randomized frames. The duration can be determined by analyzingthe frames to calculate the duration in unit time (UT) for each frame.The frames along the durations are provided to the select component 218.

The measuring components 216 are described as measuring duration,however other criteria can be measured in addition to or instead of theduration. For example, current consumption, emissions, transitions andthe like can be measured.

The frame select component 218 selects one of the frames fortransmission and attaches a seed index to the selected frame 112 toindicate which seed was used. For example, two bits can be attached tothe selected frame to designate the randomization used, such as todesignate the original frame 110 as ‘00’, the first randomized frameusing the first seed as ‘01’, the second randomized frame using thesecond seed as ‘10’ and the third randomized frame using the third seedas ‘11’.

FIG. 3 is a diagram illustrating a derandomizer receiver 300 thathandles randomized frames. The receiver 300 can be used, for example, asthe derandomizer receiver 106 in the system 100, described above. Thederandomizer receiver 300 analyzes a received frame that may berandomized and derives an output frame that substantially includes anoriginal frame.

The derandomizer receiver 300 includes a seed extractor 320, a pluralityof derandomizers 318 and a frame selector 322. The receiver 300 receivesthe received frame 112 from the transmitter 200. The seed extractor 320extracts a seed identification or index from the received frame 112. Inone example, the seed index is obtained based on a selected number ofbits assigned to the seed index. The seed extractor 320 outputs the seedindex to the frame selector 322.

The plurality of derandomizers 318 are assigned seed values thatcorrespond to the plurality of randomizers 214, described above. Thederandomizers 318 perform the opposite operation, referred to asdescrambling or unrandomizing. As a result, a first derandomizer of theplurality 318 generates a first unrandomized frame using the first seed.A second derandomizer generates a second unrandomized frame using thesecond seed. A third derandomizer generates a third unrandomized frameusing the third seed.

The frame selector 322 receives the received frame 112, the firstunrandomized frame, the second unrandomized frame and the thirdunrandomized frame and passes one of the frames as an output frame 114based on the seed index. In one example, if the seed index is ‘00’, thereceived frame 112 is passed, if the seed index is ‘01’ the firstunrandomized frame is passed, if the seed index is ‘10’ the secondunrandomized frame is passed, and if the seed index is ‘11’ the thirdunrandomized frame is passed as the output frame 114.

The output frame 114 is substantially the same as the original frame110. The output frame 114, including the fixed length and varied lengthdata, can then be used by other components.

It is appreciated that variations of the receiver 300 are contemplated.For example, a single derandomizer could be used with a seed that variesaccording to the seed index.

FIG. 4 is a diagram illustrating an example frame 400 for transmission.The frame 400 could be used for the frame 112, described above. It isappreciated that the frame 400 is an example and that variations andother forms of frames can be also be used.

The frame 400 is shown with a plurality of header fields including async field, seed index/ID, and status and data fields. It is appreciatedthat variations in the fields, lengths of the fields, omission of someof the fields, and/or other fields can be present in the frame 400.

The sync field has a duration, such as a duration of 56 UT in oneexample, and is used to synchronize the transmitter and receiver. Theseed index is a field that identifies which seed of a plurality of seedswas used to randomize. For example, a seed index of 0 could correspondto no randomization, a seed index of 1—a first seed, a seed index of 2—asecond seed, and a seed index of 3—a third seed. Generally, the seedindex has sufficient bits to convey the seed index used. The statusfield is a field that has one or more bits and is used to indicate astatus of the frame.

The data fields include a plurality of nibbles. In this example, thedata fields are designated DATA 0, DATA 1, . . . to DATA N, where N isthe number of nibbles of data present. The data fields include fixeddata and variable data, thus there is typically a minimum number of datafields. Additionally, the data fields are randomized using a seedspecified by the seed index. Also the CRC nibble is randomized togetherwith the data nibbles.

FIG. 5 is a graph 500 illustrating example simulation of frames sentusing randomized frames and non randomized frames. The graph 500 isprovided for illustrative purposes only. The graph 500 is obtained bysimulating frames and randomized frames using a communication protocol,such as SPC or SENT. The simulation uses a frame having 2 bits for seedindex and 10 nibbles.

An x axis specifies frame duration in unit time (UT) and a y-axisdepicts number of frames. A first portion 501 is based on using atransmitter that does not employ randomization. Here it can be seen thata max frame duration of 315 UT is seen.

A second portion 502 is based on a randomizer transmitter, such as therandomizer transmitter 200, described above. An average frame durationis reduced by 5.4% and a maximum frame duration of about 275 UT isreduced by 12.42%.

Thus, the addition of 2 bits for the seed index results in a substantialreduction in average frame duration and an even more substantialreduction in maximum frame duration.

FIG. 6 is a flow diagram illustrating a method 600 of transmittingframes with a reduced average duration. The method 600 randomizes framesand then identifies which frame has the lowest or shortest duration.Then, the identified frame is sent to a receiver, where the originalframe is recreated. The method 600 can be performed with arrangements,systems and variations thereof described above.

A control unit selects a plurality of seeds at block 602. The controlunit can include a processor and a memory and/or other circuitry. Thenumber of the plurality of seeds is selected to mitigate the frameduration. It is appreciated that the more seeds that are used, the morebits that are required to specify an index to the used seed. In additionto selecting the seeds, the randomization technique is also selected.For example, an additive scrambling technique, pseudo randomization,multiplicative scrambling technique and/or the like can be selected.

In addition to the number of seeds, it is also appreciated that someseeds may work better than others. Thus, in one example, possible seedsare tested for reducing frame duration and the plurality of seedsselected at block 602 are those seeds that yield the lowest averageduration. Such seed selection is typically done at system configurationand/or development. However, it is appreciated that a control unit orthe like can be used to determine or update the seeds.

A plurality of randomized frames are generated from an original frameusing the plurality of seeds at block 604. One or more randomizers, suchas the randomizers 214, can be used to generate the randomized frames.The randomizers generally utilize a different seed of the plurality ofseeds in order to generate each of the randomized frames. As a result,the plurality of randomized frames are typically varied from each otherdue to the randomization.

The plurality of randomized frames and the original frame are measuredfor duration at block 606. The duration in unit time can be generated,such as using the formula described above, to measure the duration ofeach of the frames. It is noted that some of the randomized frames canbe longer than the original frame as the randomization does not alwaysresult in shorter frames. One or more measuring components can be usedto perform the duration measurements.

It is also appreciated that other criteria in addition to or instead ofduration can also be measured. For example, current levels, emissions,transitions and the like can be measured or otherwise obtained for theplurality of frames and the original frame.

A frame of the plurality of frames and the original frame is selectedbased on the duration measurements at block 608. Typically, the shortestor about the shortest frame is selected. Additionally, it is appreciatedthat the shortest frame may be the original frame. A frame selectcomponent, in one example, is used to select the frame from theplurality of frames and the original frame. In yet another example, theselect frame is always one of the plurality of randomized frames.

It is also appreciated that the frame selection can depend on othercriteria, as described above.

A seed index is attached to the selected frame and transmitted at block610. The seed index references or identifies which of the plurality ofseeds was used to generate the selected frame. Typically, a seed indexof zero indicates that the original frame is sent as the selected frame.The control unit or frame select component can be used to attach theseed index.

The selected frame can be transmitted or sent using a variety ofsuitable techniques. In one example, the selected frame is sent using anRF signal. The selected frame can be additionally processed, includingmodulating, error checking and the like.

A receiver receives the selected frame at block 612 and extracts theseed index from the selected frame. The selected frame can be processed,such as being demodulated and the like. An extract seed component can beused to pull the seed index from a field of the selected frame. In oneexample, the seed component provides an output value that indicateswhich of the plurality of seeds was used to randomize the selectedframe.

One or more derandomizers process the selected frame at block 614 and adescrambled or unrandomized frame corresponding to the seed index isprovided. In one example, the one or more derandomizers use assignedseeds of the plurality of seeds to generate a plurality of unrandomizedframes. Essentially, the derandomizers perform the reverse or inverseoperation of the randomizers. Then, one of the plurality of unrandomizedframes correlated to the extracted seed index is selected as theprovided output frame. The output frame is typically substantiallyidentical to the original frame. The output frame can then be used forits data and/or other applications.

In another example, a derandomizer is selected based on the seed indexand is used to generate the output frame. In this example, there are aplurality of derandomizers where each has an assigned seed. In yetanother example, the derandomizer is provided with a seed based on theseed index in order to generate the output frame. It is appreciated thatother variations of generating the output frame are also contemplated.

The method 600 can be repeated for additional frames in order to provideadditional transfer of information. It is appreciated that an averageframe duration can be mitigated by using the above randomizationtechniques and selecting a frame having a shorter or shortest duration.As a result, throughput and the like can be increased.

While the methods provided herein are illustrated and described as aseries of acts or events, the present disclosure is not limited by theillustrated ordering of such acts or events. For example, some acts mayoccur in different orders and/or concurrently with other acts or eventsapart from those illustrated and/or described herein. In addition, notall illustrated acts are required and the waveform shapes are merelyillustrative and other waveforms may vary significantly from thoseillustrated. Further, one or more of the acts depicted herein may becarried out in one or more separate acts or phases.

It is noted that the claimed subject matter may be implemented as amethod, apparatus, or article of manufacture using standard programmingand/or engineering techniques to produce software, firmware, hardware,or any combination thereof to control a computer to implement thedisclosed subject matter (e.g., the systems shown above, arenon-limiting examples of circuits that may be used to implementdisclosed methods and/or variations thereof). The term “article ofmanufacture” as used herein is intended to encompass a computer programaccessible from any computer-readable device, carrier, or media. Thoseskilled in the art will recognize many modifications may be made to thisconfiguration without departing from the scope or spirit of thedisclosed subject matter.

Examples may include subject matter such as a method, means forperforming acts or blocks of the method, at least one machine-readablemedium including instructions that, when performed by a machine causethe machine to perform acts of the method or of an apparatus or systemfor concurrent communication according to examples described herein.

In one example, a transmitter arrangement using randomization isdisclosed. The arrangement includes one or more randomizers, a measurecomponent and a frame select component. The one or more randomizers areconfigured to generate one or more randomized frames from an originalframe. The measure component is configured to measure a criterion forthe original frame and the one or more randomized frames. The frameselect component is configured to select a frame for transmission fromthe one or more randomized frames and the original frame. The selectionis performed according to the measured criteria, such as frame duration.

In another example, a communication system is disclosed. Thecommunication system includes a randomizer transmitter and aderandomizer receiver. The randomizer transmitter is configured togenerate a plurality of randomized frames from an original frame,compare durations of the original frame and the plurality of randomizedframes, select a frame for transmission based on the durations andappend a seed index to the selected frame. The derandomizer receiver isconfigured to receive the selected frame, extract the seed index fromthe selected frame and descramble the selected frame using the seedindex.

In another example, a method of transmitting frames is disclosed. Aplurality of seeds are selected by a control unit. A plurality ofrandomized frames are generated from an original frame using theplurality of seeds. One of the plurality of randomized frames isselected for transmission based on frame duration.

Although the invention has been illustrated and described with respectto one or more implementations, alterations and/or modifications may bemade to the illustrated examples without departing from the spirit andscope of the appended claims. For example, although a transmissioncircuit/system described herein may have been illustrated as atransmitter circuit, one of ordinary skill in the art will appreciatethat the invention provided herein may be applied to transceivercircuits as well.

Furthermore, in particular regard to the various functions performed bythe above described components or structures (assemblies, devices,circuits, systems, etc.), the terms (including a reference to a “means”)used to describe such components are intended to correspond, unlessotherwise indicated, to any component or structure which performs thespecified function of the described component (e.g., that isfunctionally equivalent), even though not structurally equivalent to thedisclosed structure which performs the function in the hereinillustrated exemplary implementations of the invention. The component orstructure includes a processer executing instructions in order toperform at least portions of the various functions. In addition, while aparticular feature of the invention may have been disclosed with respectto only one of several implementations, such feature may be combinedwith one or more other features of the other implementations as may bedesired and advantageous for any given or particular application.

Furthermore, to the extent that the terms “including”, “includes”,“having”, “has”, “with”, or variants thereof are used in either thedetailed description and the claims, such terms are intended to beinclusive in a manner similar to the term “comprising”.

What is claimed is:
 1. A transmitter arrangement using randomizationcomprising: one or more randomizer circuits configured to generate oneor more randomized frames, respectively, from an original frame; ameasure circuit configured to measure a criterion for the original frameand the one or more randomized frames, respectively; and a frame selectcircuit configured to select a frame for transmission from the one ormore randomized frames and the original frame according to the measuredcriterion.
 2. The arrangement of claim 1, wherein the criterion is frameduration.
 3. The arrangement of claim 1, wherein the criterion iscurrent consumption.
 4. The arrangement of claim 1, wherein the one ormore randomizer circuits are assigned one or more unique seeds togenerate the one or more randomized frames, respectively.
 5. Thearrangement of claim 2, wherein the original frame has a greaterduration than at least one of the one or more randomized frames.
 6. Thearrangement of claim 1, wherein the selected frame for transmissionincludes a seed index field configured to identify whether a seed wasused and, if so, identify the seed used by the respective randomizercircuit in generating the respective randomized frame.
 7. Thearrangement of claim 1, wherein at least one of the one or morerandomizer circuits comprises a linear shift register circuit.
 8. Thearrangement of claim 1, wherein the one or more randomizer circuitsinclude at least one of an additive randomizer circuit and amultiplicative randomizer circuit.
 9. The arrangement of claim 1,wherein the criterion is frame duration, and the frame select circuit isconfigured to compare frame durations of the original frame and the oneor more randomized frames, and select one of the original frame and theone or more randomized frames based on which one has the shortestduration.
 10. The arrangement of claim 1, further comprising a datasource circuit to generate the original frame.
 11. The arrangement ofclaim 1, wherein the selected frame for transmission includes anunrandomized portion, which includes a seed index that identifieswhether a seed was used and, if so, identifies the seed used by therespective randomizer circuit in generating the respective randomizedframe.
 12. The arrangement of claim 1, further comprising a receivercircuit configured to receive the selected frame and to generate anoutput frame by unrandomizing the selected frame.
 13. A transmitterarrangement using randomization comprising: one or more randomizercircuits configured to generate one or more randomized frames,respectively, from an original frame; a measure circuit configured tomeasure a criterion for the original frame and the one or morerandomized frames, respectively; a frame select circuit configured toselect a frame for transmission from the one or more randomized framesand the original frame according to the measured criterion; a receivercircuit configured to receive the selected frame and to generate anoutput frame by unrandomizing the selected frame; and wherein thereceiver circuit is configured to: receive the selected frame, extract aseed index from the selected frame, and descramble the selected frameusing the seed index.
 14. The arrangement of claim 13, wherein thereceiver circuit comprises a plurality of derandomizer circuits eachconfigured to descramble the selected frame according to a uniqueassigned seed to generate a plurality of unrandomized frames.
 15. Thearrangement of claim 14, wherein the receiver circuit comprises a frameselect circuit configured to select one of the plurality of unrandomizedframes according to the extracted seed index.
 16. A transmitterarrangement using randomization comprising: one or more randomizercircuits configured to generate one or more randomized frames,respectively, from an original frame; a measure circuit configured tomeasure a criterion for the original frame and the one or morerandomized frames, respectively; a frame select circuit configured toselect a frame for transmission from the one or more randomized framesand the original frame according to the measured criterion, wherein thecriterion is frame duration; and wherein the frame select circuit isconfigured to select a number of the plurality of randomized frames toreduce an average frame duration.
 17. The arrangement of claim 16,wherein at least one of the one or more randomizer circuits comprises alinear shift register circuit.
 18. The arrangement of claim 16, whereinthe one or more randomizer circuits include at least one of an additiverandomizer circuit and a multiplicative randomizer circuit.
 19. Thearrangement of claim 16, further comprising a data source circuit togenerate the original frame.